The present invention relates to a web handling system and in particular to an apparatus and a method for feeding a continuous web from a roll or a box or other web storage means to an entry point of a machine that utilizes the web as source material. More particularly, the invention relates to an apparatus and a method for aligning to an entry point of a converting line a continuous web from a roll or a box or other web storage means wherein at least some of web layers are not aligned with each other, but are off-set or overlapped laterally to form a width of the web storage means that is wider than the web width.
It has been conventional practice in manufacturing disposable absorbent products, such as diapers, sanitary napkins, etc., to supply converting lines with source materials, such as plastic film webs and non-woven webs, in a form of straight-wound rolls wherein layers of web are wound on a core substantially perpendicular to the core axis of rotation. Therefore, straight-wound rolls usually provide webs that are in a well aligned condition. Feeding these web from straight-wound rolls into converting lines often involves some type of unwinding apparatus generally used in the art to unwind the web from the roll at a controlled web velocity and tension. However, modern source materials that may be used on converting lines often cannot be fed by conventional means because the modern source materials may not be suitable for winding onto straight-wound rolls.
Modern source materials may be more complex than conventional webs and may include various product elements incorporated into conventional webs. For example, modern source materials for disposable absorbent articles, may include fastening tapes, side panels, cuffs, core components, waist strips and/or other product elements attached to a carrying web. Also, modern source materials may include various modifications of the web surface(s) affecting the thickness and/or surface texture of the web, for example, embossing, selfing, slitting, etc. Further, modern source materials may include various lines of weakness, for example, perforations, channels, etc., to enable subsequent splitting of the web into separate parts along the lines of weakness during converting and/or tearing the final product along the lines of weakness by a consumer. Also, modern source materials are often pre-fabricated off converting lines in order to maintain or reduce the number of process operations on converting lines which can increase the cost of production and the cost of new product upgrades.
As a result of the complexity related to such modern source materials, the pre-fabricated materials may be considerably thicker than conventional webs, and/or have uneven thickness, shape and strength properties. The thickness and/or texture of pre-fabricated materials may be susceptible to compression forces that may be found inside of ordinary wound rolls and which may result in irreversible damage to the material. Further, the lines of weakness which may be present in pre-fabricated materials may be susceptible to tensions that may cause the material to tear along the lines of weakness at inappropriate times. These problems can make prefabricated materials less suitable for winding onto rolls and, particularly, for winding onto straight-wound rolls. Although some of the possibly damaging forces can be reduced or controlled by limiting the length of material wound on a roll (because larger rolls have usually higher compression forces), such a reduction will also reduce the period of time between roll changes on a converting line. Consequently, the cost associated with providing uninterrupted supply of the material to the converting line will increase.
One alternative to straight-roll winding is traverse winding of rolls, wherein a web is wound not perpendicularly to the axis of rotation but in layers across the width of the roll forming a web source structure that is wider than the web width. Each consecutive layer may be wound on top of the preceding layer in a direction which is opposite to the lateral direction of winding of the preceding layer. The turns of material may be off-set laterally in relation to each other or overlapped laterally. Because the traverse-wound rolls may provide a desired length of web at reduced outside diameters of web on the roll than straight-wound rolls holding the same length of web, many of the negatives described above can be avoided. However, because the web on the traverse-wound roll is not aligned perpendicularly to the core axis, the web does not unwind into an aligned web path which extends between the core and the entry point of the converting line. Instead, the web unwinds laterally across the core forming web paths which are not aligned to the entry point of the converter. The degree of misalignment of the web may prevent the use of conventional means for aligning the web.
Another alternative to straight winding is festooning into a container. For example, the continuous web may be folded back and forth within the container. In some case it may be most economical or practical to festoon the web such that the folds are off-set laterally along the width of the container forming a web source structure that is wider than the web width. Like the turns of the web in traverse-wound rolls, the festoon folds may be spaced apart laterally in relation to each other or overlapped laterally. However, contrary to the roll-wound web, either straight-wound or traverse-wound, the festooned web may be subjected to little or no tension. This characteristic of festooning can make festooning suitable for storing webs that are susceptible to excessive compression forces and/or excessive tensions that may be present in the wound rolls.
Festooning may be also beneficial for webs which may be difficult to splice automatically between roll changes. Festooning enables the web to be spliced manually by attaching the end of the web from a first festooned container to the beginning of the web from a second festooned container. The containers can be disposed adjacent to each other.
However, the festooned web arranged laterally in a wide container may present problems. One problem, as it was described above for the traverse-wound rolls, may relate to relatively significant misalignment between the web paths exiting the festooned container toward the entry point of the converter. Another problem may relate to the festooned web having little or no tension and may require introduction of a tension force in the web in order to make the web manageable for alignment with the entry point of the converting line.
Accordingly, it would be desirable to provide an apparatus and a method for aligning to an entry point of a converting line a web which is stored in a web source structure that is wider than the web width. It would also be desirable to provide an apparatus and a method for aligning to an entry point of a converting line a web which is stored in a web source structure wherein at least some of the web layers are off-set laterally in relation to each other or overlapped laterally. It would also be desirable to provide an apparatus and a method for aligning to an entry point of a converting line a web which is stored in a web source structure wherein the web is subjected to little compression forces. It would also be desirable to provide an apparatus and a method for aligning to the entry point on the converting line a web which is stored in a web source structure wherein the web is subjected to little or no tension.
The present invention provides an apparatus and a method for aligning a continuous web with a point of entry of a machine adapted to accept the web. The point of entry has a machine centerline and the web has a web width, a longitudinal centerline, a first surface and a second surface. The apparatus includes an input guide having an input guide outer surface which is situated to intersect a web extending from a web source structure toward the entry point of the machine. The input guide outer surface is wrapped at least partially by the first surface of the web when in use. The apparatus further includes a centering guide having a centering guide concave portion which is situated to intersect with the web extending from the input guide toward the entry point of the machine. The centering guide concave portion is wrapped at least partially by the second surface of the web when in use. The apparatus further includes an output guide having an output guide concave portion which is situated to intersect with the web extending from the centering guide toward the point of entry of the machine. The output guide concave portion is wrapped at least partially by the first surface of the web when in use.